Watery asteroids may explain why life is 'left-handed'

Published: Tuesday, March 17, 2009, 11:04 [IST]

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London, March 17 (ANI): A new study has suggested that watery asteroids hurtling through the solar system gave a boost to left-handed proteins on Earth, which explains why life on our planet is 'left-handed'.

Curiously, almost every living organism on Earth uses left-handed amino acids instead of their right-handed counterparts.

According to a report in New Scientist, the new research suggests that water on asteroids amplified left-handed amino acid molecules, making them dominate over their right-handed mirror images.

In the 1990s, scientists found that meteorites contain up to 15 percent more of the left version too.

That suggests space rocks bombarding the early Earth biased its chemistry so that life used left-handed amino acids instead of right.

"Meteorites would have seeded the Earth with some of the prebiotic compounds like amino acids that are needed to get life started, and also biased the origin of life to the left-handed amino acid form," said Daniel Glavin at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Some have suggested that polarized starlight preferentially destroyed right-handed amino acids on asteroids.

But, this alone couldn't explain why the meteorite bias is so strong.

Now, Glavin and colleague Jason Dworkin have shown that water amplified the asymmetry.

They studied an amino acid called isovaline in six meteorites that showed evidence of ancient exposure to liquid water for about 1000 to 10,000 years.

The longer water persisted in the rock, the stronger its left-handed isovaline bias, the team found. (ANI)